cls 2215 principles of immunohematology hemolytic disease of the newborn hdn

CLS 2215 Principles of

Immunohematology

Hemolytic Disease of the Newborn

HDN

Hemolytic Disease of the Newborn

• HDN occurs when the Mother has an antibody capable of crossing the placental barrier that is specific to an antigen present on the red blood cells of the fetus.

• Fetal red cells become coated with the IgG alloantibody and undergo accelerated destruction both before and after birth.– Where does the baby get an antigen that is

foreign to the Mom?

• It’s the Dads fault!

Mechanism of HDN

Immunization and Production of Antibody

1. Fetomaternal Bleed:

2. During subsequent pregnancies:

Categories of HDN

1. Rh System Antibodies

2. Other Blood Group Antibodies

3. ABO Antibodies

1.

2.

3.

Pathophysiology of HDN

• Accelerated red cell destruction leads fetus to increase production of RBCs therefore there are increased numbers of nucleated RBCs.

Severe cases of HDN can result in:• Generalized edema of the fetus:

• Severe anemia:

Pathophysiology of HDN

Bilirubinemia• Results from increased RBC destruction

• Fetus in utero:

• Newborn:

Prenatal Testing

Patient History: • Which pregnancy is this?

• Has she ever been transfused?

• Is she Rh negative? Has she had antenatal RhIg?

• Does she have a previously identified unexpected antibody?

Prenatal Testing

Test Mom for ABO, Rh (Weak D), and Antibody Screen

Group O Mom :

Rh Negative Mom:

Prenatal Testing

Positive Antibody Screen? • Identify antibody and perform titration

if antibody is clinically significant (anti-D, K, etc.). FREEZE the serum sample. If a subsequent titer is requested you need to compare the first titer results with the second titer. Run both titers in parallel and compare endpoints. • Has the titer increased? Two tube increase is

clinically significant. May lead to more sensitive testing to determine severity of disease.

Rh Immune Globulin

What is it?

• How does it work?

Rh Immune Globulin

• Full Dose:

• Mini dose:

When to give RhIg

Antenatal administration

Amniocentesis

When to Give RhIg

Postpartum Administration• When Mother is Rh negative (and is negative

for anti-D) and Baby is Rh positive. It is that simple.

• How much?

Rosette Test

• Purpose:

• Qualitative:

Rosette Test - Principle• Add chemically modified anti-D to Mothers

washed Post Partum (EDTA) red cells and incubate at 37oC. Anti-D will attach to Rh Positive cells present.

• Wash cells and add R2R2 indicator cells. Indicator cells will “rosette” around anti-D that has attached to the Rh positive cells.

• Centrifuge and resuspend the suspension and read microscopically looking for Rosettes.

• Rosettes present?

Kliehauer Betke (Acid Elution)

• Purpose:

• Quantitative:

Kliehauer Betke (Acid Elution)

• Principle: Draw a Post Partum EDTA sample from the mother and make and fix a blood smear on a glass slide. Flood the smear with an acid solution. The Hgb of adult red cells is washed out by the acid solution while red cells with Hgb F are not. Counter stain (Safranin) the smear. Cells with Hgb F stain red while the adult red cells remain transparent.

• Count number of stained Hgb F red cells within 2000 adult (Hgb A) red cells.

Kliehauer Betke StainCalculations

• # Fetal cells / 2000 adult cells x 100 = % of Fetal cells present in the maternal circulation.

• % of Fetal cells X 50 = number of mls of Fetal bleed

• # of mls of fetal bleed / 30 = # vials of RhIg required

Cord Blood StudiesRequired testing on the Cord Blood of

Newborn’s with Rh Negative Moms (suggested on Group O Moms)

• ABO group:

• Rh typing:

• Direct Antiglobulin Test:

Exchange Transfusion

• Exchange transfusion may be definitive therapy for newborns with severe HDN.

• A process where you exchange baby red cells with transfused red cells. Accomplishes the following:• Remove coated RBCs

• Remove antibody

• Lower bilirubin:

Compatibility testing for Exchange Transfusion

• Crossmatch blood for exchange transfusion with Mothers serum. Why?

• Can crossmatch with baby if mom is not available, but best indication of red cell survival is to crossmatch with the Mothers serum. Remember the source of the antibody is…

Which mothers are candidates for RhIg?

• Mother Rh positive with anti-K • Baby Rh positive with negative DAT

• Mother O negative with anti-C• Baby A negative with positive DAT

• Mother A negative with negative IAT• Baby O positive with negative DAT

Which mothers are candidates for RhIg?

• Mother: A negative with anti-D, C, K– Baby: B positive, +DAT eluate showed D, C

• Mother: A negative with negative IAT– Baby: O positive with positive DAT, eluate neg

• Mother: AB negative with anti-D– Baby: A negative with negative DAT